"I have been taking bets on the Pope and the Archbishop of Canterbury for as long as I care to remember," William Hill spokesman Graham Sharpe said, denying that gambling on the papal succession was blasphemous.

"It's fair to say that this is the first papal punt to be decided in the full internet betting era," he added, noting the growth of online gambling could make for a more lively market.

"It's not going to rival the Champions League [soccer] but it will produce enough turnover to make it worth doing."

Cardinal Arinze and Pope Benedict, who was then Cardinal Joseph Ratzinger, were both among the bookmakers' favourites in 2005 when the German was elected to succeed Pope John Paul II, Mr Sharpe said.

Two outsiders on the Paddy Power list of contenders showed the Irish bookmaker's customary eye for a publicity stunt.

Dark horses included the British scientist and atheism campaigner Richard Dawkins on 666/1 and fictional Father Dougal McGuire, a hapless priest from the 1990s Irish TV comedy show Father Ted on 1000/1, the same odds as U2 front man Bono.